In a chromatographic analysis, it has been said that the time and effort required for the so-called pre-treatment, including sampling, extraction of an analyte, and sample preparation such as concentration represents 80% of the analytical work. Solid-Phase-Micro extraction (SPME) developed by Pawliszyn in 1990 is a method for pre-treating a sample, where such works and introduction into the chromatograph can be simply performed. In the SPME method, a fiber whose surface is coated with a liquid phase is exposed to a headspace or a solution of the sample in order to perform extraction, and an analyte extracted into the fiber liquid phase is thermally desorbed at a injection port during GC and is introduced to the GC (Japanese Patent Laid-Open No. 5-506715).
In addition, an In-tube SPME method in which a capillary column of GC is used for an adsorption mechanism (Hiroyuki Katayama, Shizuo Narimatsu, Heather L Lord, J. Pawliszyn Chromatography 20 (1999) 237-249) has been used recently. In this method, a sample is made to flow into the capillary column and a liquid phase in the column is allowed to retain the analyte, then the solvent is made to flow therethrough for desorbing the analyte by the use of the solvent. On the other hand, another method has been suggested in which a syringe is used and an analyte is retained by a hollow needle having a stationary phase being fixed on an inner surface of the hollow needle, then the analyte is desorbed by making a solvent flow through the needle or by heating the needle (Japanese Patent Laid-Open No. 8-94597). Conventionally, when the analyte is concentrated, a column whose cylindrical body is packed with a bead-like inorganic filler has been generally used.
In the former technique, a sample retention capacity is generally increased by making a thickness of the fiber liquid layer larger, in order to increase a sample capacity. However, there is a problem that the time required for equilibrating the analyte with the liquid phase becomes longer as the film thickness is increased. As for extraction of an agricultural chemical dissolved in water which is performed by actually using a liquid phase having a thickness of 100 μm, it has been frequently reported that the time required for reaching an equilibrium was 15 to 60 minutes or more (J. Beltram, F. J. L pez. F. Hern ndez Journal of Chromatography A. 885 (2000) 389-404). Although the equilibration time has been reduced by stirring the sample and by shaking the syringe or heating the sample for example in order to reduce the equilibration time, substantial reduction in the equilibration time has not been achieved (Makoto Okawa, Takashi Kasamatsu, Yoshiya Akiba, the 8th Symposium on Environmental Chemistry, Kyushu, 1999). In addition, this method cannot be applied to an analysis of a thermally decomposable component because the sample is thermally desorbed when the sample is introduced into the analytical system. When the thermal desorption in the SPME is performed at an injection port of an existing gas chromatograph, a peak width is finally broadened because a low boiling component largely diffuses at a time of its injection.
In the In-tube SPME method using a capillary column as well as in the In-tube SPME method using a syringe, a stationary phase is provided on an inner surface of the hollow needle and a center thereof is hollow. The sample freely passes through the hollow portion, thus, opportunities that the analyte diffuses into the stationary phase are reduced, and the time required for reaching an equilibrium becomes longer. In addition, it becomes necessary to increase an inner diameter of the needle and to increase the film thickness, in order to increase a sample capacity. However, as the inner diameter increases, a contact efficiency is reduced due to an extended diffusion time. Further, in a method which uses a column being packed with a filler, there are some problems as follows: (1) a flow rate depends on the packing state, so that analytical values will vary; and (2) resistance to a stream of the fluid becomes larger and the flow rate per unit time is decreased, so that the analytical time becomes longer. In this method, thermal desorption is also carried out at an existing GC injection port, so that broadening of a peak width cannot be avoided.
Therefore, an object of the present invention is: to increase a sample capacity relative to that obtained by the conventional capillary column; to reduce a distribution resistance relative to that obtained by a column packed with particulate substances; and to reduce a time required for reaching a distribution equilibrium of an analyte compared with that obtained by the conventional SPME or In-tube method, by the use of a porous body having an integral structure of open cell structures (a so-called monolithic structure) when a pre-treatment for introducing a sample into a chromatograph is performed. The present invention is widely applicable to pre-treatments of a gas chromatography, a high-performance liquid chromatography, and other analytical methods.